Forcing Firefox Extensions to Work on Newer Versions

One of the biggest issues people have with Mozilla/Firefox extensions (besides security vulnerabilities) is the required version field that indicates which versions of Mozilla/Firefox that particular extension will run on. While that may at first seem a nifty feature, anyone familiar with Firefox’s release of development builds, ranging from a build every hour to a build every night, will immediately realize the problem: the extensions aren’t configured to work with the new builds! And extension writers don’t always have time to update their works with new whitelists of permitted FF builds; and so they don’t work! But fret not, there is a solution, and if you are addicted to to the bleeding edge and set your download manager to download and run the builds on the hour (like some I know…) then this is for you!

  1. Access the Firefox “registry” by directing FF to “about:config,” without the quotes or comma obviously.
  2. Right-click anywhere on that page, and select New -> String.
  3. In the message box that pops up, enter “app.extensions.version” for the name (no quotation marks….) and press enter;
  4. And when another box appears prompting you for the value, enter the version number of the FF build you want it to impersonate when installing a plugin. I recommend 1.5, but you can use 1.0 as well.
  5. That’s it, you’re done.. Close the tab and surf our archives, install your plugins, and enjoy your new-found liberty!

This “hack” works on all versions of Firefox and on all operating systems. Please keep in mind that forcing a extension to work can result in trouble, but it is highly unlikely, most will fail gracefully.

Also, if you attempted to install an extension before doing this, it will not install because Firefox remembers that this extension is not compatible and does itself a “favor” and doesn’t check. In such a case either modify the wrapper for the XPI file, or clear your profile and try again.

A common example of this hack “failing” to work is an upgrade to Bon Echo from a FF installation with extensions. In such a case, or any other time you attempted to install a plugin on Bon Echo and it failed before performing this hack:

  1. Browse to the Bon Echo settings folder located in X:\Documents and Settings\Local Settings\Application Data\
  2. Delete that folder.
  3. Browse to the Bon Echo folder at X:\Program Files\Bon Echo\ and clear the “Extenions” subfolder of all files.
  4. Restart your PC
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  • 20 thoughts on “Forcing Firefox Extensions to Work on Newer Versions

    1. so tell us, howdowe modify the wrapper? When you have installed extensions when you upgrade you can not so this either. The extensions that are installed are the ones I want to use.

    2. Doesn’t work for me…It checks for compatibilityupdates even after I add the new string…

    3. Hack failed for me. Set field value to 1.5 and tried to install Flashblock on Portable apps Bon Echo alpha.  No dice. 

    4. There's a typo in there – should be "app.extensions.version" (missing "n") – well at least that's the string that worked for me! 

    5. Wanted to add my 2 cents. Cut to the chase, I got my extensions to work with the Nightly Builder Tools extension at

      I tried the steps at the top of this page – going into the about:config and making the settings changes. It did not work for me, it might for others. So I read through the replys and then clicked on the link above and installed the “nightly tester”.xpi extension

      1st you have to download Bon Echo whatever build and then install the nightly tester tool extension. After installing and restarting Bon Echo, you must go back into where your extensions and themes are located – under Tools — “Add-Ons”, click on the button that says “make all compatible”, after the system or extension does it’s magic, restart Bon Echo and now your extensions should be working.

      I have removed and then added some other extensions in Bon Echo 2.0a3 build. When you are installing a new extension there is a option that you must check to allow the nightly tester extension to override the non-compatability between the extensions and Bon Echo.
      This should do the trick and your extensions will work. I like the way Bon Echo looks and is working so far.

    6. yo this works for bon echo 2.0 a but i upgrade to 2.0b2 and it doesn’t work now… anyone know what to do??

    7. Help me please…
      I just installed Firefox 2.0, and all of a sudden, my username/password isn't being inserted in the signon window (it always was before). I tried the usual suspects–I did not mistakenly tell FF not to remember the password for this site; and I also tried the remember password bookmarklet, but all to no avail–FF will not ask me to remember this password. What do I need to do to get around this?

    8. Please add firefox cookies/bad web sites immunization in next version!
      Firefox 2 cannot reject third party cookies!!!!!!!!

    9. This does not provide instructions on fixing this on the MAC OS.  I have no idea how this works.

    10. I have found that since BonEcho and Firefox share the same extensions folder, I just opened up firefox and installed Google Notebook.  Closed Firefox, opened BonEcho – and it works!  (on the Mac)

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